1. Field of the Invention
The present invention relates to a backlight assembly, and more particularly, to a backlight assembly including at least one light emitting diode (LED) as a light source and a liquid crystal display (LCD) module using the backlight assembly.
2. Discussion of the Related Art
Recently, flat panel display (FPD) devices that have the advantage of light weight, thin profile, and low power consumption have been commonly utilized as substitutes for cathode ray tube (CRT) devices. In general, display devices may be classified, depending on the abilities for self-emission, into emissive display devices and non-emissive display devices. The emissive display devices display images by self-emitting light, whereas the non-emissive display devices require a light source because they do not emit light by themselves. For example, plasma display panel (PDP) devices, field emission display (FED) devices, and electroluminescent display (ELD) devices are commonly utilized as emissive display devices. Liquid crystal display (LCD) devices may be regarded as non-emissive display devices although some applications do not require a light source. The LCD devices are usually installed in notebook and desktop computers because of their high resolutions, color display capabilities, and high quality images.
The LCD device includes an LCD module consisting of an LCD panel for displaying images and a backlight assembly for supplying light to the LCD panel. In general, the backlight assembly may be regarded as either side-type backlight assembly or direct-type backlight assembly depending to the disposition of the light source. With the great demand for the LCD device having a large display screen, the direct-type backlight assembly including a plurality of light sources has become more popular to provide more light. The light source of the backlight assembly may be discharge lamps, such as cold cathode fluorescent lamps (CCFL), external electrode fluorescent lamps (EEFL), and the like. Recently, the light emitting diode (LED) has been widely utilized as the light source for the backlight assembly to improve color reproducibility and to increase display brightness.
FIG. 1 is a schematic exploded perspective view of an LCD module 1 according to the related art. As shown in FIG. 1, the related art LCD module 1 includes an LCD panel 10 that includes two substrates (not shown) facing each other and a liquid crystal layer (not shown) interposed between the two substrate, a gate printed circuit board (PCB) 18 and a source PCB 16 arranged respectively at the edges of the LCD panel 10, a backlight assembly 20 arranged under the LCD panel 10, a main frame 40 surrounding the LCD panel 10 and the backlight assembly 20, a bottom frame 50 arranged under the backlight assembly 20 and combined with the main frame 40, and a top frame 60 covering the LCD panel 10 and combined with the main frame 40 and the bottom frame 50.
The backlight assembly 20 includes a plurality of PCBs 22 on an inner surface of the bottom frame 50. Here, the plurality of PCBs 22 are disposed in a row and spaced apart from each other. Moreover, each row of PCBs 22 is provided with a plurality of LEDs 24 arranged in a row. In other words, the row of PCBs 22 including the plurality of LEDs 24 is repeatedly disposed on the bottom frame 50. The backlight assembly 20 also includes a reflective sheet 26 disposed on the PCBs 22, the LEDs 24, and the inner surface of the bottom frame 50. Specifically, the reflective sheet 26 is formed with a plurality of holes 28 corresponding to the respective LEDs 24. The LEDs 24 pass through the holes 28, thereby being exposed from the reflective sheet 26. Here, the PCB 22 is connected to a backlight driving circuit (not shown) and signals from the backlight driving circuit is applied to the LEDs 24 through a thin film line (not shown) on the PCB 22 so that the LEDs 24 are able to emit red, green and blue light. Therefore, a white light is obtained by uniformly mixing the red, green and blue light.
The backlight assembly 20 also includes a transparent window 30 disposed on the reflective sheet 26. The transparent window 30 is formed with a plurality of diverters 31 corresponding to the respective LEDs 24. Moreover, a diffusion plate 32 for creating uniform brightness is disposed on the transparent window 30. An optical sheet group 34 is disposed on the diffusion plate 32 such that the optical sheet group 34 consisting of a plurality of optical sheets are sequentially layered. When light from the LEDs 24 is emitted directly or by reflective sheet 26, the red, green and blue color lights are uniformly mixed. The uniformly mixed light has uniform brightness by the diffusion plate 32, and then the light is incident into the LCD panel 10 after passing through the optical sheet group 34, thereby displaying a desired image.
However, there is a structural limitation in the related art. Each row of PCBs 22 is formed with the plurality of LEDs 24 disposed thereon to emit a predetermined color, which depends on that row of PCBs 22 to drive the LEDs 24. If only a few of the LEDs 24 are defective, it is difficult to selectively replace the defective LEDs 24, and the whole row of PCBs 22 with the defective LEDs 24 has to be replaced with a new one. As a result, many non-defective LEDs 24 on the PCBs 22 are wasted, thereby lowering productivity and increasing the product costs.